Environmentalists in Canada and the U.S. say they are cynical about reports of a prime ministerial appeal to the White House for common North American greenhouse-gas emissions standards in the oil and gas sector.

CBC News revealed Friday that Prime Minister Stephen Harper sent a letter to U.S. President Barack Obama last month formally proposing "joint action to reduce greenhouse-gas emissions in the oil and gas sector" to help speed approval for the controversial Keystone XL pipeline.

Harper's message offers a clear sign of Ottawa's willingness to make concessions in order to get the presidential green light for TransCanada Corp.'s $7-billion pipeline, which will connect the Alberta oilsands to refineries in Texas.

Details of the letter are not public, and it's not known whether Harper made any concrete offer.

The Prime Minister's Office is refusing to confirm a letter was sent, but says harmonizing emissions policies with the U.S. has long been a government goal.

A Harper spokesman says the two countries already have integrated oil and gas economies "which underscores the importance of continuing to work together to reduce greenhouse-gas emissions."

Talk of a quid-pro-quo on Keystone has been circulating since the beginning of the year, when Obama signalled his intention to ramp up his climate change agenda.

But Canadian officials have repeatedly denied any deal was in the works. Even now, a spokesman for Natural Resources Minister Joe Oliver claims no knowledge of the Harper-Obama letter, as do industry players.

Still, sources say Harper has often told his cabinet he intends to fulfil Canada's international commitments on climate change while moving cautiously for fear of alienating Alberta.

Act of desperation

Environmentalists are characterizing any offer from Canada's Conservative government as an act of desperation to save a pipeline that Harper once called a "no-brainer."

A statement from 350.org, a group of international climate-change activists, described the reported overture as "a last-ditch bait-and-switch by the Canadian government."

And the Sierra Club of Canada and Greenpeace Canada both said any Canadian promises on climate change ring hollow after years of government inaction.

But even as Harper indicates flexibility to Obama, the domestic negotiations are heading in the opposite direction. Springtime talk of "40-40" — requiring producers to improve their emissions intensity by 40 per cent, with a $40-per-tonne penalty — has now been whittled down to 30-30, with governments under pressure from industry. A final agreement is still in limbo.

Analysts have said even the 40-40 scenario wouldn't meet Canada's emissions targets, a point not lost on the Americans.

And Obama has said any approval for the Keystone pipeline would depend on minimizing emissions.

The United States is currently on track to meet its 2020 target for greenhouse-gas emissions reductions, while Canada's current trajectory would leave the country 50 per cent short of its promised goal, even though Canada has a long-standing policy of mirroring the U.S. emissions regime.

Critics point out that any pipeline that increases the export capacity of oil-sands production will only make it more difficult for Canada to meet its greenhouse-gas emissions targets.